Fix recent regression filling in flavor extra_specs

In commit cb338cb7692e12cc94515f1f09008d0e328c1505, we dropped an extra
DB query to fill in flavor extra_specs because the object should already
have those set. However, if we pulled the flavor from the instance,
extra_specs are mostly not stored, which means we effectively cut off
the scheduler filters from access to those things.

This adds that back in for that case, but only temporarily. Soon we will
be merging a change to stash real flavor objects with the instance, which
will make this moot. However, that may take a while to merge and this is
broken now.

Change-Id: Ia728025345b09687da9744004f0f47ad73ce196c
Closes-Bug: #1403547
Merge "Fix recent regression filling in flavor extra_specs"